Since the first days of electronics, analog adjustments in resistances for some circuit and system designs have typically been necessary. Initial conventional techniques involved making resistive adjustments by physically replacing resistors and swapping resistor values on circuit boards, which was a typically slow, laborious process that was prone to reliability issues. Later, other conventional approaches included the use of adjustable potentiometers that altered resistance values by changing a mechanical setting, such as turning a shaft that altered the contact points. However, these mechanically adjustable potentiometers still required manual intervention to calibrate settings to obtain the desired resistance value. As such, setting the resistance value was still a manual process, which typically was slow, labor intensive, and relatively prone to error. These adjustable potentiometers usually were also subject to resistive changes caused by vibration.
Integrated circuit technology has enabled potentiometers to digitally select establish variable resistive paths. Once a specific resistance is set, the settings for the resistive path are made permanent. Using conventional techniques, this can be done by setting select pins to a particular value or by programming the settings using fuse or non-volatile technology, such as EEPROM technology, to store the value. While digitally selectable techniques remove the manual-related processes, conventional implementations of non-volatile methodology typically require high voltages that, in turn, require large charge pumps, which consume relatively large amounts of die area. Typically, EEPROM technology has a relatively higher failure rate than is desired. In addition, the programming time for typical non-volatile memory technologies is relatively long, thereby hindering the rates at which resistances are adjusted and set. Further, in conventional techniques, the resistance values are set by design, which is typically limited to combinations of discrete resistance values.
There are continuing efforts to improve digital potentiometer technology.
Although the previous drawings depict various examples of the invention, the invention is not limited by the depicted examples. It is to be understood that, in the drawings, like reference numerals designate like structural elements. Also, it is understood that the depictions in the FIGS. are not necessarily to scale.